It doesn't matter if not all android users have upgraded, it is what is going on now. People are migrating and all new phones being sold since 2019 from major carriers and phone manufacturing were starting to default to Google and Google has made so anyone can use RCS by downloading the message app.
Just so we are on the same page, i use iPhone and several times a week, Apple deprecates my iMessage to SMS even when im texting someone on iMessage, mid conversation it switches back and forth. All these but Google sucks and RCS doesn't work is nonsense. iMessage doesn't work properly.
That's right, there is a green bubble issue within Apple's own ecosystem. No Android involved.